There are already known numerous pyrethroid insecticides, some of which combine a good insecticide activity with a sufficient persistence in the field, for instance, "Synthetic Pyrethroids" by M. Elliot--Editors ACS Symposium, Series No. 42, Washington, 1977.
Likewise, there are known pyrethroids substituted in position 3 of the cyclopropylic ring by a dienic chain.
M. Elliot and collaborators have described 5-benzyl-3-furyl-methyl-esters of 2,2-dimethyl-3-butadienyl-cyclopropanecarboxylic acid. See NATURE, No. 244, p. 456 (1973).
These compounds, which are endowed with a high degree of insecticidal activity, rapidly undergo degradation in the presence of air and light (photooxidation), however, and because of this they are not suited for the use in agriculture.
In Japanese Patent Application No. 7411854 by Sumitomo, reported in Chemical Abstracts No. 81, 34599 (1974), there are described esters with lower alcohols of 2,2-dimethyl-3-cyclopropanecarboxylic acids substituted in position 3 by a branched dienic chain having from 4 to 8 carbon atoms and not substituted by halogen.
In Belgian Pat. No. 858,137 (Bayer), there is described a method for the synthesis of intermediates for pyrethroids, among which are esters of 2-(.beta.,.delta., .delta.-trichloro-1,3-dienyl)-2,2-dimethyl-cyclopropanecarboxylic acid.
However, examples of the preparation of this acid nor of its derivatives have not been given, nor has there been indicated the insecticidal properties or its characteristics.
From the process described in the aforementioned patent, there can be deduced that the above-mentioned carboxylic acid should be prepared starting from 1,1,3-trichloro-6-methylheptatriene. No indications are given regarding the preparation of this compound or of other trienes, nor is there said anything about their use in the synthesis of pyrethroids.